I lay on my sides, and have to switch sides often as well. Occasionally I wake up on my belly, or on my back, and I feel a little guilty about it so switch right away. We have one of those feather mattresses on top of our bed, and a fitted feathered mattress cover on top of that. There is a nice probably permanent indentation where I sleep, where the feathers have pushed themselves up into a personalized, comfy, body fitting pillows. I may HATE this after baby is here... but it has been wonderfull destroying them during the pregnancy.
Maybe you could get a couple body pillows, one for each side. You could wrap yourself around them and get the pressure off your hips... The have those mommy sized maternity pillows, but they looked pricey.
I sure hope you find a comfy way to rest so that you can be refreshed and ready for the sleepless nights with your LO during your baby moon!